Drag block and slip assembly

ABSTRACT

This invention relates to a slip and drag block assembly for use with a packer or bridge plug, for example, in the casing of an earth well. The drag block elements are spring loaded and held within a slotted tubular cage member which is a casting. The slip elements, spring loaded, are pivoted from the drag block elements and are held in position by the tubular cage. Setting of the slips is by movement of the cone assembly of the packer or bridge plug, for example. Insertion of the drag block elements into the cage is accomplished by means of a rotatable tubular ring contiguous to the drag block end of the cage and having a notch in its end facing the cage whereby each drag block element is inserted in a slot in the cage as the notch in the rotatable ring is aligned therewith. The notch is then successively rotated to the next cage slot assembly for insertion of the drag block element. After the drag block elements are inserted, the rotatable ring is secured with the notch located between a pair of cage slot arrays. Because the slip elements are pivoted from the drag block elements, the outward movement required to set the slips is the same regardless of the weight rating of the nominal size of the casing used, thus providing a more nearly equal bite of the teeth in the casing wall than would occur if the slip elements were pivoted from the cage.

United States Patent 1 Pitts 1 Jan. 16,1973

[54] DRAG BLOCK AND SLIP ASSEMBLY [75] Inventor: Charles A. Pitts, Wichita Falls, Tex.

[73] Assignee: The Dow Chemical Company,

Midland, Mich.

[22] Filed: June 21, 1971 211 Appl. No.: 154,955

[52] US. Cl ..166/216, 166/140 [51] Int. Cl. "E2lb 23/06, E2lb 33/129, E2lb 43/10 [58] FieldofSearch ..166/138,140,2l0,2l6,217

Primary ExaminerDavid H. Brown Attorney-Earl D. Ayers et al.

[57] ABSTRACT This invention relates to a slip and drag block assembly for use with a packer or bridge plug, for example, in the casing of an earth well.

The drag block elements are spring loaded and held within a slotted tubular cage member which is a casting. The slip elements, spring loaded, are pivoted from the drag block elements and are held in position by the tubular cage. Setting of the slips is by movement of the cone assembly of the packer or bridge plug, for example.

Insertion of the drag block elements into the cage is accomplished by means of a rotatable tubular ring contiguous to the drag block end of the cage and having a notch in its end facing the cage whereby each drag block element is inserted in a slot in the cage as the notch in the rotatable ring is aligned therewith. The notch is then successively rotated to the next cage slot assembly for insertion of the drag block element. After the drag block elements are inserted, the rotatable ring is secured with the notch located between a pair of cage slot arrays.

Because the slip elements are pivoted from the drag block elements, the outward movement required to set the slips is the same regardless of the weight rating of the nominal size of the casing used, thus providing a more nearly equal bite of the teeth in the casing wall than would occur if the slip elements were pivoted from the cage.

5 Claims, 3 Drawing Figures DRAG BLOCK AND SLIP ASSEMBLY BACKGROUND OF THE INVENTION This invention relates to a slip and drag block assembly for use with a packer or bridge plug, for example, in earth wells.

The use of packers in the earth well industry is well known. Packers are typically utilized in a well casing to divide the interior of the easing into two zones, that is, a zone below the packer and a zone above the packer. Packers are run into well casings on the lower end of a string of tubing. When the packer has been lowered to the desired position in the well casing, means is provided for setting the packer, that is, fixing it into position and expanding a packing element to seal the interior of the casing to divide the easing into the two mentioned zones.

Slip and drag block assemblies are commonly employed as the means for setting the packer in its predetermined position in the well casing.

One problem in connection with slip and drag block assemblies is economic, e.g., the high cost of machining and assembly of the parts of the devices.

Another problem is that of keeping the teeth of the slip elements in a position parallel to the casing wall to be engaged by the teeth. While this problem has in certain instances been solved, the higher production costs of such assemblies is, as mentioned above, an economic problem in a highly competitive industry.

Accordingly, a principal object of this invention is to provide an improved slip and drag block assembly.

Another object of this assembly is to provide an improved, more economical to manufacture, slip and drag block assembly.

Still another object is to provide a slip and drag block combination wherein either the slip or the drag block may be replaced independently of the other.

A further object of this invention is to provide an improved slip and drag block assembly in which the slip biting elements are parallel with the casing wall.

STATEMENT OF THE INVENTION In accordance with this invention there is provided a slip and drag block assembly which is adapted to be disposed adjacent to and in alignment with a packer or bridge plug unit which is to be set at a predetermined location along and within a string of casing in an earth well, for example.

The invention comprises, disposed around an inner tube-like mandrel, a tubular cage assembly having spring loaded drag block elements extending through slots in the wall of the cage. An array of slip elements, each having an elongated bar-like pivot arm and each one being pivotally coupled to a drag block element at a point near the upper end of the drag block element, and spring loaded with respect thereto by a spring bearing on said pivot arm and by a spring disposed adjacent to the end of said drag block element which is remote from the toothed end of the slip element, and is held in predetermined two dimensional position by the cage assembly unit. The tapered underside of each slip element is urged outwardly by the advancing tapered cone surface of the packer or bridge plug as the packer or bridge plug is being set in position in a cylindrical area such as a string of easing, tubing, pipe or borehole.

BRIEF DESCRIPTION OF THE DRAWINGS The invention, as well as additional objects and advantages thereof, will best be understood when the following detailed description is read in connection with the accompanying drawing, in which:

FIG. 1 is a side elevational view, partly broken away and in section, of apparatus in accordance with this invention,

FIG. 2 is a sectional view taken along the line 22 of FIG. 3, and

FIG. 3 is an enlarged sectional view of the slip and drag block assembly of FIG. 1.

Referring to the drawing, there is shown an assembly, indicated generally by the numeral 10, in accordance with this invention, comprising an upper mandrel l2 and a lower mandrel 14 coupled together in end-to-end relationship by means of threads 16. A packer assembly, indicated generally by the numeral 18, is threadedly coupled to the lower end of the lower mandrel 14 by threads 20. The upper end of the packer assembly 18 comprises a cone element 22 whose inner surface abuts against a detent 24 in the outer surface of the lower mandrel 14.

An elongated sleeve part, indicated generally by the numeral 26, has a thick walled lower part 28 and a thin walled upper part 30 and extends over the upper mandrel l2 and lower mandrel 14 at the upper part thereof.

The upper end of the thick walled lower part 28 has a threaded rod-like element 32 extending into a so-called .l-slot 34 whose long arm part is parallel to the longitudinal axis of the lower mandrel 14.

The sleeve 26 fits slidably around the upper mandrel l2 and lower mandrel 14.

A cage part, indicated generally by the numeral 36, is generally tubular in configuration and has a threaded upper end part 38 by means of which it is rigidly mechanically coupled to the lower end of the thick walled lower part 28 of the sleeve 26.

The cage part 36 is fabricated by casting, machining or injection molding to have an outer wall part 40 and a shorter inner wall part 42 extending axially downwardly from the threaded end part 38.

The outer wall part 40 contains an array of slots 44, which are symmetrically disposed in side-by-side relationship around the periphery of the cage part 36.

Each of the slots, indicated generally by the numeral 44, contains a drag block element 48 which is an elongated block-like element having an upper bearing surface 49 having beveled upper end edge surfaces 50, 52 and outwardly extending flanges 54, 56 extending from the lower end parts thereof. Each drag block element 48 contains two spring receiving bores 58, 60, extending inwardly from its bottom surface 64. The bore 60 is disposed near the flange 56. The thickness of the element 48 is less from a point near the bore 60 to the end having the flange 54. A generally U-shaped recess 62 extends across the edge part lying between the bottom surface 63 and the bottom surface 65 of the less thick part of the drag block element 48.

The drag block elements 48 are held in position against a retaining ring 68 which covers the end of the slots 44 which faces the flange 56 and against a retainer 67 on the slip element 78 at the end having the flange 54. A spring 70, fitted into bore 60 and bearing against the inner cage wall 42, holds each drag block element 48 in a spring loaded outward position in the cage, aided by spring 72 in bore 58 which bears against the pivot bar 71 ofa slip element 78. v

V The ring 68, which holds the flanges 56 of the drag block elements 48 in position in the cage part 40, contains a notch 74 whose width and length correspond to the width and at least the length of the flanges 56. The ring 68 is rotated to align the notch 74 with each slot 44. After the drag block is inserted with the flange 54 under the retainer 67, the ring 68 is rotated to align the notch with another slot. After all the drag block elements 48 are all mounted in the cage 36, the ring 68 is rotated until the notch 74 lies between a pair of slots 44 and is then secured in position by means of the screw 76, for example.

A slip element, indicated generally by the numeral 78, is pivotally mounted in an arcuate groove on the underside of each drag block element 48.

Each slip element 78 has a teeth bearing upper surface part 80 which extends below the cage 36 and a lower end surface 82 which is tapered upwardly towards the lower end of the slip element 78, the taper being adapted to match the mating taper of the conical part 22 of the packer assembly 18. The pivot bar part 71 of the slip element 78 is an elongated bar-like part having a rounded end which mates with the U-shaped recess 62.

A bar-like element 88 extends upwardly from the pivot bar part 71 adjacent to the end of the slot 44, carrying the laterally extending bar-like retainer 67.

The spring 72 extending into the bore 56 and bearing against the upper surface of the pivot bar part 71, presses the slip element downwardly towards the lower mandrel 14 as the slip and drag block assembly is being lowered down the casing 92.

OPERATION In operation, as the assembly is lowered down the casing, the .l-mechanism is held with the element 32 in the cross slot position so there is no relative movement between the packer assembly and the slip and drag block assembly. The drag block elements 48, each urged outwardly by its springs 70, 72, ride in frictional dragging contact along the casing 92 until the location is reached where the packer assembly is to be set, e.g., expanded to seal off the casing except for flow through the inner mandrel and tubing usually attached above and perhaps below the apparatus shown in FIG. 1.

When the slips are to be set against the casing, the tubing (not shown, but coupled to the upper end 91 of the upper mandrel 12 at the threads 92) is rotated to move the element 32 into the vertical part of the .I-slot 34.

Tension is placed on the upper mandrel l2 and the packer assembly, attached to the inner mandrel 14, moves upwardly with respect to the drag block elements 48 which are held in position by friction at least until the conical part 22 of the packer assembly 18 forces the slips 78 outwardly to engage the teeth 80 with the wall of the casing 93.

Once the teeth 80 of theslip elements 78 bite into the casing wall, the conical surface 22 is advanced further to bring all of the teeth 80 into vbiting position with respect to the wall of the casing, and the limited friction of the drag block elements 48 is no longer necessary to set the slips.

Continued tension on the tubing above the apparatus 10 after the slips 78 are set expands the packer (or bridge plug) and seals off the annulus between the lower mandrel and the wall of the casing.

The tubing above the assembly 10 is continuously held under tension after the packer is expanded by a second set of slips located at a suitable control head (not shown), for example.

When the packer is to be released and recovered from the casing, tension on the tubing is released and the element 32 is moved up the J -slot into the side position (by rotation of the tubing). This movement releases the packer and withdraws the conical part 22 sufficiently from underneath the slip elements 78 to allow them to retract from the wall of the casing.

If the space around the slip elements 78 is filled with sand, rust, or any particulate matter, liquid may be circulated through the annulus between the tubing and the casing and thence between the sleeve 30 and cage 36 to wash such materials from the apparatus. Jarring of the slip and drag block assembly, with the element 32 in the vertical slot of the J-mechanism is also helpful to loosen the assembly 10.

Because the cage assembly 36, drag block elements 48 and slip elements 78 may readily be made by casting, require little skill on the part of workmen doing further machining and assembly of the parts, this slip and drag block assembly is, though very effective and efficient for the purpose it is to beused, economical to produce. Further, any parts worn or damaged in use may easily be replaced in the field.

Because the slip elements 78 are pivotally mounted on the drag block elements 48 whose position is predetermined with relation to the inside diameter of any weight casing used, the slips maintain a parallel position to provide an even bite of all their teeth 80 against the casing wall.

The assembly is also well suited, as stated above, to be cleaned by circulating liquid through it to dislodge and wash away particulate materials.

The device of the invention has been described as a tension actuated device. If the apparatus were reversed end to end, however, the packer could be set by compression means rather than tension as described herein; the slip and drag block assembly would function equally well in an inverted position.

What is claimed is:

1. An earth well tool assembly comprising a tube-like inner mandrel having a first end, a second end and a side wall, a device having a frustoconical surface disposed contiguously with the second end of said mandrel with the smaller diameter of said frustoconical surface facing towards said first end of said mandrel, a slip and drag block assembly disposed adjacent said frustoconical surface and including a hollow generally cylindrically shaped cage member having a shorter inner wall and a. spaced apart longer outer wall, the outer wall having an array of longitudinally disposed slots disposed symmetrically around the periphery thereof, each of said slots having a casing wall contacting part of a drag block element protruding therethrough, each drag block element having an elongated block-like body with end flanges extending lengthwise from the lower edges of its ends, each of said drag block elements being spring loaded between itself and said inner wall of said cage near the end thereof farther from said frustoconical surface, one of said end flanges being retained in said longer slot by ring means, the lower surface of the end of said drag block element which is farther from said frustoconical surface being substantially below the lower surface of the remainder of the drag block element as measured from near the point of said spring loading to the other end of the drag block element, a laterally extending U- shaped groove, said groove being disposed in the under surface of said drag block element adjacent to the point of said spring loading, a plurality of slip members each having a toothed part and a bar-like mounting part including a rounded end and an upwardly extending protuberance spaced from said toothed part, said protuberance having a flange element extending towards said drag block element, said slip member having said rounded end of said bar-like mounted part disposed in said U-shaped groove, the other of said end flanges of said drag block element being disposed under said flange on said protuberance, said protuberance extending through said slot through which said contacting part extends, means for spring loading said slip member with respect to said drag block element, said toothed part of said slip members facing outwardly from said inner mandrel with an opposed tapered surface thereof adapted to bear against said frustoconical surface.

2. Apparatus in accordance with claim 1, wherein said spring loading between said drag block element and the inner wall of said cage is a coil spring which extends into a recess in said drag block element and bears against said inner wall.

3. Apparatus in accordance with claim 1, wherein the length of said bar-like mounting part is approximately the same as the length of said slip member.

4. Apparatus in accordance with claim 1, wherein the means to spring load said slip member with respect to said drag block element comprises a coil spring seated in a second recess in the undersurface of said drag block element and bearing against said bar-like mounting part.

5. An earth well tool assembly comprising a tube-like inner mandrel having an upper end, a lower end and a side wall, a device having a frustoconical surface, said device being rigidly coupled to the lower end of said mandrel with the smaller diameter of said frustoconical surface facing towards said upper end of said mandrel, a sleeve having an upper end, lower end and side walls and a slip and drag block assembly, said sleeve and said assembly being rigidly joined together in end-to-end relationship over said mandrel, said mandrel having a slot in the wall thereof adjacent to said sleeve and said sleeve having a protuberance extending into said slot, said slip and drag block assembly being disposed between the lower end of said sleeve and said frustoconical surface and including a hollow generally cylindrically shaped cage member having a shorter inner wall and a spaced apart longer outer wall, the

outer wall having an array of longitudinally disposed ing art of a drag block element protruding there hrough, each drag block element having an elongated block-like body with end flanges extending lengthwise from the lower edges of its ends, each of said drag block elements being spring loaded between itself and said inner wall of said cage near the end thereof nearest to said sleeve, one of said end flanges being retained in said longer slot by a notched rotatable ring extending around said cage member, said ring being adjacent to but spaced from said sleeve, the lower surface of the end of said drag block element which is nearer said sleeve being substantially below the lower surface of the remainder of the drag block element as measured from near the point of said spring loading to the other end of the drag block element, a laterally extending U-shaped groove, said groove being disposed in the under surface of said drag block element adjacent to the point of said spring loading, a plurality of slip members each having a toothed part and a bar-like mounting part including a rounded end and an upwardly extending protuberance spaced from said toothed part, said protuberance having a flange element extending towards said drag block element, said slip member having said rounded end of said bar-like mounted part disposed in said U-shaped groove, the other of said end flanges of said drag block element being disposed under said flange on said protuberance, said protuberance extending through said slot through which said contacting part extends, means for spring loading said slip member with respect to said drag block element, said toothed part of said slip members facing outwardly from said inner mandrel with an opposed tapered surface thereof adapted to bear against said frustoconical surface. 

1. An earth well tool assembly comprising a tube-like inner mandrel having a first end, a second end and a side wall, a device having a frustoconical surface disposed contiguously with the second end of said mandrel with the smaller diameter of said frustoconical surface facing towards said first end of said mandrel, a slip and drag block assembly disposed adjacent said frustoconical surface and including a hollow generally cylindrically shaped cage member having a shorter inner wall and a spaced apart longer outer wall, the outer wall having an array of longitudinally disposed slots disposed symmetrically around the periphery thereof, each of said slots having a casing wall contacting part of a drag block element protruding therethrough, each drag block element having an elongated block-like body with end flanges extending lengthwise from the lower edges of its ends, each of said drag block elements being spring loaded between itself and said inner wall of said cage near the end thereof farther from said frustoconical surface, one of said end flanges being retained in said longer slot by ring means, the lower surface of the end of said drag block element which is farther from said frustoconical surface being substantially below the lower surface of the remainder of the drag block element as measured from near the point of said spring loading to the other end of the drag block element, a laterally extending U-shaped groove, said groove being disposed in the under surface of said drag block element adjacent to the point of said spring loading, a plurality of slip members each having a toothed part and a barlike mounting part including a rounded end and an upwardly extending protuberance spaced from said toothed part, said protuberance having a flange element extending towards said drag block element, said slip member having said rounded end of said bar-like mounted part disposed in said U-shaped groove, the other of said end flanges of said drag block elemEnt being disposed under said flange on said protuberance, said protuberance extending through said slot through which said contacting part extends, means for spring loading said slip member with respect to said drag block element, said toothed part of said slip members facing outwardly from said inner mandrel with an opposed tapered surface thereof adapted to bear against said frustoconical surface.
 2. Apparatus in accordance with claim 1, wherein said spring loading between said drag block element and the inner wall of said cage is a coil spring which extends into a recess in said drag block element and bears against said inner wall.
 3. Apparatus in accordance with claim 1, wherein the length of said bar-like mounting part is approximately the same as the length of said slip member.
 4. Apparatus in accordance with claim 1, wherein the means to spring load said slip member with respect to said drag block element comprises a coil spring seated in a second recess in the undersurface of said drag block element and bearing against said bar-like mounting part.
 5. An earth well tool assembly comprising a tube-like inner mandrel having an upper end, a lower end and a side wall, a device having a frustoconical surface, said device being rigidly coupled to the lower end of said mandrel with the smaller diameter of said frustoconical surface facing towards said upper end of said mandrel, a sleeve having an upper end, lower end and side walls and a slip and drag block assembly, said sleeve and said assembly being rigidly joined together in end-to-end relationship over said mandrel, said mandrel having a slot in the wall thereof adjacent to said sleeve and said sleeve having a protuberance extending into said slot, said slip and drag block assembly being disposed between the lower end of said sleeve and said frustoconical surface and including a hollow generally cylindrically shaped cage member having a shorter inner wall and a spaced apart longer outer wall, the outer wall having an array of longitudinally disposed slots disposed symmetrically around the periphery thereof, each of said slots having a casing wall contacting part of a drag block element protruding therethrough, each drag block element having an elongated block-like body with end flanges extending lengthwise from the lower edges of its ends, each of said drag block elements being spring loaded between itself and said inner wall of said cage near the end thereof nearest to said sleeve, one of said end flanges being retained in said longer slot by a notched rotatable ring extending around said cage member, said ring being adjacent to but spaced from said sleeve, the lower surface of the end of said drag block element which is nearer said sleeve being substantially below the lower surface of the remainder of the drag block element as measured from near the point of said spring loading to the other end of the drag block element, a laterally extending U-shaped groove, said groove being disposed in the under surface of said drag block element adjacent to the point of said spring loading, a plurality of slip members each having a toothed part and a bar-like mounting part including a rounded end and an upwardly extending protuberance spaced from said toothed part, said protuberance having a flange element extending towards said drag block element, said slip member having said rounded end of said bar-like mounted part disposed in said U-shaped groove, the other of said end flanges of said drag block element being disposed under said flange on said protuberance, said protuberance extending through said slot through which said contacting part extends, means for spring loading said slip member with respect to said drag block element, said toothed part of said slip members facing outwardly from said inner mandrel with an opposed tapered surface thereof adapted to bear against said frustoconical surface. 